This invention relates generally to a converter of the rate of flow of a fluid, which can be applied to measurement of the consumption of liquids and gases in the chemical and pharmaceutical industries and, more particularly, for recording the consumption of liquid fuel in motor vehicles.
U.S. Pat. No. 3,867,840 (1975) discloses a known converter of the rate of flow of a fluid having an external casing with inlet and outlet holes, in which casing is formed a cylindrical measuring chamber with tangential inlet and axial outlet. Inside the cylindrical measuring chamber is disposed, on bearings, a turbine wheel with three blades arranged at angles of 120.degree.. The outer surface of the cylindrical measuring chamber is provided with longitudinal protrusions of triangular cross-section, while a photoelectric converter of frequency of rotation into electric signals is disposed in the plane of rotation of the turbine blades.
Operation of this converter is based upon the realization of a linear dependence between the frequency of rotation of the turbine wheel and the rate of flow of the measured fluid achieved by producing local hydraulic resistances by means of the protrusions of the cylindrical measuring chamber.
However, this known converter possess many disadvantages. These include the strong dependence of the error of measurement upon the density and the temperature of the measured fluid; the limited range of measurement due to the turbulence in the fluid flow when its velocity increases in the cylindrical measuring chamber; the complex shape of the cylindrical measuring chamber with protrusions; the number, configuration, and location of the protrusions, depending upon the parameters of the measured fluid, as well as the presence of a considerable dynamic error when measuring a pulsating flow of the fluid.
In another known converter of the rate of flow of a fluid, disclosed in U.S. Pat. No. 4,011,757 (1977), the design of which is somewhat analogous, a damper of the pulsations of the fluid flow is added. This damper is composed of an inlet chamber and an outlet chamber separated by a flexible membrane with a rigid center. The inlet chamber is connected hydraulically to the tangential inlet of the cylindrical measuring chamber, whereas the outlet chamber is connected to its axial outlet. In its initial position, the flexible membrane is pressed by a spiral spring against the face of the inlet hole of the converter, thus, partially closing the latter. By means of the pulsation damper, a smoothening is achieved of the pulsations of the fluid flow entering the cylindrical measuring chamber of the converter.
The disadvantage of this converter is the insufficient degree of smoothening of the pulsations of the fluid flow.